In recent years, endoscopic examination or treatment of pancreaticobiliary diseases such as biliary tract cancer, pancreas cancer, cholelithiasis and choledocholithiasis, for example, has been widely spreading in the field of medicine. These have the advantages of being less invasive and imposing less strain on patients than conventional surgical treatment.
As one method for these examination and treatment, for example, there is known ERCP (Endoscopic Retrograde Cholangio-Pancreatography). The ERCP is a diagnosis method using an endoscope to inject contrast medium into the biliary tract or the pancreatic duct and photograph that portion with a fluoroscope. In the method of injecting the contrast medium, first, an insertion part of the endoscope is inserted into the duodenum. Then, a cannula (thin tube) is fed from a forceps exit of the insertion part, the cannula is inserted from the major duodenal papilla selectively into the biliary tract or the pancreatic duct, a contrast medium is injected into the biliary tract or the pancreatic duct through the cannula, and that portion is photographed with a fluoroscope.
Moreover, a method of confirming the presence or absence of a site of stenosis inside the biliary tract or the pancreatic duct, sampling and examining cells or tissues (cytodiagnosis and biopsy), removing calculi, or the like is also known, which is performed by inserting the insertion part of a thin endoscope, generally called cholangioscope or pancreatoscope, into the biliary tract or the pancreatic duct.
Under these circumstances, when the insertion part of the endoscope is inserted into a body cavity, an insertion assisting tool for an endoscope (also called “overtube” or “sliding tube”) is used together. As one example of the insertion assisting tool for an endoscope, PTL 1 discloses one including a tubular body used as a guide through which an insertion part of an endoscope is passed, an opening part through which a distal end of the insertion part can be passed, the opening part being provided on a distal end side of a sidewall portion of the tubular body. According to this insertion assisting tool for an endoscope, when the insertion part of the endoscope is inserted into a body cavity, it is made possible by performing insertion in a state where the insertion part is covered with the tubular body easily, to perform insertion operation of the insertion part while preventing excessive bending or flexing of the insertion part. Moreover, when the distal end of the insertion part is fed from the opening part of the sidewall portion of the tubular body to be guided into a body cavity (for example, into the biliary tract), the insertion part can be easily put forward into a deep portion in the body cavity by performing the insertion while the insertion part is received and supported on an edge portion of the opening part.
Moreover, PTL 2 discloses one including an inflatable and deflatable balloon that is positioned more distally than the opening part formed in the sidewall portion of the tubular body. According to this insertion assisting tool for an endoscope, after the insertion part covered with the tubular body as mentioned above, is inserted up to a desired position in the body cavity, by inflating the balloon so as to come into close contact with an inner wall of the body cavity, the opening part of the sidewall portion can be held at a desired position (for example, at a position opposite to the major duodenal papilla). Moreover, when the distal end of the insertion part of the endoscope is fed from the opening part and the distal end of the insertion part is made into a J-shape and guided onto a proximal end side of the insertion part (for example, into the biliary tract), since the insertion part is guided while received and supported on an upper face of the balloon, the insertion part can be easily put forward.